1. Technical Field
The present disclosure relates to an electronic pen acting as a position designator designating a position to a position detection circuit, and a position detection system made up of the electronic pen and a device that includes the position detection circuit.
2. Description of the Related Art
A large number of information terminals such as tablet personal computers (PC) each equipped with a touch panel are commercially available today. The touch panel is an electronic component that combines a display unit such as a liquid crystal display with a position detection circuit that uses a touch sensor (coordinate detection sensor). When touched by finger of an operator, the touch panel permits diverse input operations. Where more detailed input operations are needed, an electronic pen is often used as a dedicated position designator. A device called a digitizer is also used extensively today. The device acts as an input device for the PC and is made up of a board that incorporates a touch sensor for position detection and an electronic pen that designates positions.
In conferences, meetings, and seminars, it is now practice to display necessary information on a screen using an information terminal and a projector, the information terminal permitting simple and quick input of information using an input device that incorporates touch sensor technology. The information terminal and the projector enable the screen to display prepared materials as well as information that may be added on the spot using the electronic pen so that the displayed information may be shared easily by all the participants at the gathering. The electronic pen may be expanded with additional functions such as a laser pointer function. The electronic pen with its laser pointer function may then be used to point to and explain the information that is projected onto the screen after being input through the information terminal using the electronic pen.
Expansion of the electronic pen with additional features such as the laser pointer function is often accomplished by putting the expanded function into a unit that is attached to the rear end of the electronic pen (opposite end to the stylus), with the electronic pen body left unchanged structurally. That is, the expanded function is configured to be housed in an enclosure separate from and attachable to the electronic pen (i.e., offered as a separate unit). When attached to the electronic pen, the separate unit provides the pen with the expanded function in a simplified manner. The techniques for incorporating the expanded function such as the laser pointer function into the electronic pen are disclosed, for example, in U.S. Patent Application Publications Nos. 2014/0028635 and 2014/0002422, and U.S. Pat. No. 7,161,578.
There are two types of electronic pen: signal oscillation type and resonance type. The signal oscillation type of electronic pen causes an oscillation circuit in the electronic pen to oscillate and transmit signals for position detection. The resonance type of electronic pen allows a resonance circuit in the electronic pen to resonate with an external magnetic field coming from a position detection circuit and to reflect signals to that circuit for position detection. The resonance type of electronic pen may store drive power inside the electronic pen by means of a resonance action with the external magnetic field. The signal oscillation type of electronic pen, by contrast, needs to have a power supply in the electronic pen to drive an oscillator and other parts.
A power supply also needs to be installed in the expanded function unit attached to the electronic pen. For example, if the expanded function is a laser pointer, relatively large power is needed to drive a semiconductor laser in the pointer. That means the power supply such as a primary or secondary battery needs to be mounted in the laser pointer. However, if the power supply is included in the expanded function unit attached to the rear end of the electronic pen, the center of gravity is shifted toward the rear end of the electronic pen. The shifted center of gravity may prevent the writer's writing pressure from being suitably propagated to a stylus of the electronic pen, causing the writer to have difficulty writing.
The signal oscillation type of electronic pen needs two power supplies: one in the electronic pen and the other in the expansion device. If the power supply of the electronic pen is exhausted, the electronic pen function cannot be used while the expanded function is still usable. That means the user is required always to manage the power supplies in both the electronic pen and the expanded function. If primary batteries are used as the power supplies, both the electronic pen and the expansion device need to be structured to let their primary batteries be replaced. This may put structural constraints on these devices.
Furthermore, the expansion device is equipped with an operation switch while the electronic pen to be connected with the unit has a cylindrical enclosure. It follows that operating the switch applies pressing force perpendicularly to the axial direction of the cylindrical electronic pen. This can overburden a connector between the electronic pen and the expansion device, rendering the connector liable to break.